function show2(a, b, c) {
    c = c || 0.6;
    return (a + b) * c;
}
console.log(show2(1, 2, 3));
// 可选参数也可以使用附初始值
function get(a, b, c) {
    if (c === void 0) { c = 6; }
    return (a + b) * c;
}
console.log(get(1, 2));
